System and Method for Filling a Hydrogen Storage Vessel at Enhanced Flow Rates

ABSTRACT

A compressed gas delivery vehicle has a cooling system that cools an interior of a gas storage vessel during filling of the vessel with the gas wherein the gas is sorbed by a sorbent material comprising an adsorbent or an absorbent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/870,655, filed Dec. 19, 2006.

BACKGROUND

Current methods and equipment for delivering hydrogen gas to customers include pipelines, compressed gas trucks (tube trailers), liquid hydrogen tanks, as well as compressed gas cylinders, alone or packed in cylinder bundles. In the case of pipelines, hydrogen is transferred from production plants to industrial plants that consume large amounts of hydrogen. These types of pipelines are limited to large industrial basins where this delivery method is economical. In the case of tube trailers, compressed gas can be discharged into a compressed gas stationary storage system, such as a compressed gas tank or a bank of cylinder bundles. In the case of delivery using cylinders, cylinders or cylinder bundles are simply unloaded from a vehicle onto the customer storage area. In the case of liquid hydrogen, the liquid is usually transferred to a stationary liquid tank at the customer facility.

A typical compressed hydrogen installation at a customer facility can be made of two cylinder bundles with 100 to 250 Nm³ of hydrogen depending on local industrial practice. One cylinder bundle will typically occupy a surface of 1 meter×1 meter, and the installation comprising the two bundles and space necessary to load them to, and unload them from, a truck will have a typical footprint of 1 meter×4 meters, excluding security fencing and surface free from any structure according to applicable regulations.

Storage of hydrogen in metal hydride (or other hydrogen-absorbing materials) tanks offers a much higher volumetric density than compressed gas. This type of storage has been demonstrated in several research and development efforts, one application of which includes the supply of hydrogen to fuel cells in military submarines. However, it is not practical to store hydrogen in metal hydride tanks onboard trucks for delivery because of the low gravimetric storage density of known hydrogen-absorbing materials. One of the requirements of these types of storage tanks is that they include a cooling/heating subsystem for cooling the hydrogen-absorbing material upon filling and heating it upon discharge, because the heat of hydrogen absorption must be removed during filling and the heat of desorption must be provided during discharge.

As an example of the storage capacity afforded by metal hydrides, FeTiH₂ can contain approximately 1000 Nm³ of hydrogen per cubic meter of material, Even with the cooling path and heat exchange material inserted, the volumetric density of stored hydrogen can be much higher. 200 liters of hydrogen-absorbing material is sufficient to store 200 Nm³ of hydrogen. The heat of absorption of hydrogen in FeTi is approximately 30 kJ/mol H₂ or 0.37 kWh/Nm³H₂.

In a scenario where hydrogen in a stationary storage device using a hydrogen-absorbing material is consumed slowly between refills but where filling must be done quickly for economical reasons, cooling rate becomes the limiting factor. There are several examples of metal hydride storage technologies with means of heat transfer, including those found in: U.S. Pat. No. 3,943,719 (hydride-dehydride power system); U.S. Pat. No. 4,016,836 (hydride tank on-board a motor vehicle with heat transfer between the vehicle's radiator and the hydride tank); U.S. Pat. No. 6,182,717 (process for filling a metal hydride tank on-board a vehicle with heat transfer between the vehicle's tank and the filling station's stationary metal hydride tank; U.S. Pat. No. 6,918,430 (on-board metal hydride storage in vehicles with heat transfer system); U.S. Pat. No. 6,860,923 (on-board metal hydride storage in vehicles with heat transfer system); US 2005-0139493 (on-board metal hydride storage in vehicles with heat transfer system); and US 2004-0042957 (thermal hydrogen compressor using metal hydrides).

SUMMARY

There are disclosed a method and system for filling a gas storage vessel wherein a cooling system is associated with the vehicle transporting the compressed gas with which the vessel is filled.

One method of filling a gas storage vessel includes the following steps. A compressed gas is allowed to flow from a compressed gas storage tank borne by a compressed gas delivery vehicle to a gas storage vessel where it is sorbed by a sorbent material contained therein, wherein the gas storage vessel is not borne by the vehicle. A primary coolant fluid is allowed to flow through a primary coolant path circulating between the gas storage vessel and a primary cooling system borne by the vehicle thereby cooling the sorbent material.

The method may include one or more of the following aspects:

-   -   the sorbent material is a metal hydride and the gas is hydrogen.     -   the gas is silane and the sorbent material is a zeolite.     -   a secondary coolant flow path extends between an internal         combustion engine of the vehicle and a vehicle radiator and said         primary and secondary coolant flow paths do not fluidly         communicate.     -   a secondary coolant flow path extends between an internal         combustion engine of the vehicle and the primary cooling system         and the primary cooling system is a vehicle radiator.     -   first and second valves are provided that are adapted and         configured to selectively allow flow of the primary coolant         through the primary coolant flow path or the secondary coolant         flow path and the first and second valves are actuated to place         them in orientations that either allows a flow of the primary         coolant through the primary coolant flow path or the secondary         coolant flow path, or allows a flow of the primary coolant         through the primary coolant flow path or the secondary coolant         flow path.     -   allowing a flow of hydrogen from the hydrogen storage vessel to         a stationary hydrogen consumption device, wherein said         stationary hydrogen consumption device is not borne by the         vehicle.     -   the primary coolant is pumped by a pump utilizing electrical         power while an internal combustion engine used to propel the         vehicle is not running.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

FIG. 1 is a schematic of one embodiment of the disclosed system including heat transfer between the storage tank and an auxiliary radiator.

FIG. 2 is a schematic of another embodiment of the system including heat transfer between the storage tank and a radiator of the vehicle.

FIG. 3 is a schematic of a portion of the embodiment of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

For convenience, Table I recites descriptions of all the reference characters in the Figures.

TABLE I Reference Characters Used in Figures  1 vehicle  3 compressed gas container  4 compressed gas container outlet conduit  5a cooling system outlet valve  5b cooling system outlet conduit  5c chilled coolant fitting  5e gas storage vessel coolant inlet valve  6 chilled coolant outlet conduit  7a cooling system inlet valve  7b cooling system inlet conduit  7c warm coolant fitting  7e gas storage vessel coolant outlet valve  8 warm coolant inlet conduit  9a compressed gas outlet valve  9b compressed gas outlet conduit  9c compressed gas fitting  9e hydrogen storage vessel inlet valve 11 gas storage vessel heat exchange conduit 13 gas storage vessel 15 cooling system heat exchange conduit 17 cooling system 19 internal combustion engine 20 hydrocarbon fuel tank 21 radiator 25 second radiator valve 27 radiator heat exchange conduit 31 first radiator valve 32 second radiator hose 33 first radiator hose

In the field of gas storage, adsorption is a process that occurs when a gas accumulates on the surface or in pores of a solid, forming a molecular or atomic film (the adsorbate). On the other hand, absorption is a physical or chemical phenomenon or a process in which atoms, molecules, or ions enter some bulk phase of gas, liquid or solid material. Absorption is a different process from adsorption, since the molecules are taken up by the volume, not by surface. Either of these two processes will release heat of enthalpy because the atoms, molecules, or ions reach a lower energy state when absorbed or adsorbed. Conversely, energy must be supplied to the sorptive material in order to desorb the atoms, molecules, or ions.

When gas is supplied to a sorptive material within a storage vessel, the heat of enthalpy released increases the temperature of the material. As the temperature of the material increases, continued sorption of the gas by the material becomes more difficult. For practical purposes, it is desirable to fill such a vessel relatively quickly. So, the pressure of the gas being supplied to the vessel must be increased over time in order to maintain a desired rate at which the vessel is filled with the gas, as the temperature inside the vessel increases over time. Thus, heat transfer out of the storage vessel is usually the limiting factor in achieving a desirable filling time and filling rate.

One solution is to remove heat from the vessel being filled. This is typically achieved by flowing coolant fluid through a heat exchange conduit within the sorptive material and some sort of cooling device permanently associated with the vessel. However, this necessitates that a cooling device be provided with each storage vessel thereby increasing the capital cost. Additionally, the footprint of the vessel would also be increased, thereby requiring additional costs for civil engineering, concrete pad construction and fencing, depending on local requirements.

In order to avoid both of these problems, there are disclosed a method and system for filling a gas storage vessel wherein a cooling system is associated with the vehicle transporting the compressed gas with which the vessel is filled. One important advantage of such a solution is that a single cooling system on the vehicle can be used for frequent filling operations at several customer locations on a delivery route. Thus, there would be no need to invest in one cooling system for each and every storage vessel. If the vessel is infrequently refilled, such as in a fuel cell system for electrical power backup, removing the need to invest in a cooling system only for use with the storage vessel is especially economical.

Generally, the current method and system may be performed with any combination of adsorbent material and gas that exhibits reversible adsorption. One of ordinary skill in the art will recognize that the patent literature is replete with descriptions of adsorbents that reversibly adsorb gases and their details need not be replicated here in full. However, non-limiting examples of adsorbent material include activated carbon, zeolite materials, activated alumina, aluminosilicates, silica gel, and porous glass. Non-limiting examples of gases used with an adsorbent include hydride and halide gases, such as silane, diborane, propane, methane, natural gas, germane, ammonia, stibine, hydrogen sulfide, hydrogen selenide, hydrogen telluride, and corresponding and other halide (chlorine, bromine, iodine, and fluorine) gaseous compounds such as NF₃, and organometallic Group V compounds such as (CH₃)₃Sb.

Also generally speaking, the current method and system may be performed with any combination of absorbent material and gas that exhibits reversible absorption. One of ordinary skill in the art will recognize that the patent and non-patent literature is replete with descriptions of absorbents that reversibly absorb gases and their details need not be replicated here. However, one particularly preferred combination of gas and absorbent material is that of hydrogen and a metal hydride. Non-limiting examples of metal hydrides include Mg₂NiH₄, NaAlH₄, LaNi₅H₆, MgH₂, FeTiH₂, Na₃AlH₆, CaNi₅H₆, and LaNi₄H₆, and other advanced metal hydrides believed to reversibly absorb hydrogen such as Li₃AlH₆₁ LiMg(AlH₄)₃, LiNH₂—MgH₂, and K₂LiAlH₆.

In the case of hydrogen, the storage vessel may itself be part of a more complex energy system at a customer location where it is connected to a stationary hydrogen consumption device not borne by the vehicle. One example is a regenerative energy system comprising photovoltaic(s) panel(s) and/or wind mill(s) for supplying electricity, an electrolyzer, and a fuel cell. Hydrogen produced by the electrolyzer is stored in the storage vessel. When the electrical power output of the photovoltaic(s) panel(s) and/or the wind mill(s) is insufficient for the demand, the fuel cell consumes hydrogen and air (or oxygen) to produce a supplemental or alternative supply of electricity.

As best illustrated in FIG. 1, in one embodiment a vehicle 1 has an onboard compressed gas container 3 and an onboard cooling system 17. During a filling operation, gas from compressed gas container 3 flows through compressed gas container outlet conduit 4, compressed gas outlet valve 9 a and into compressed gas outlet conduit 9 b. A compressed gas fitting 9 c connects conduit 9 b and a gas storage vessel inlet valve 9 e. One of ordinary skill in the art will recognize that fitting 9 c (as well as fittings 5 c, 7 c) comprises the combination of devices permanently attached to the end of conduit 5 b and inlet valve 5 e that are adapted to provide a gas-tight seal between conduit 5 b and valve 5 e. As the gas is sorbed by sorbent material contained in gas storage vessel 13, heat is generated.

In order to achieve a relatively fast fill rate, a cooling system 17 is employed with the gas storage vessel 13. A coolant fluid is chilled at cooling system 17 while traversing cooling system heat exchange conduit 15. Chilled coolant is pumped out of the cooling system 17 via cooling system outlet valve 5 a and into cooling system outlet conduit 5 b. A chilled coolant fitting 5 c connects cooling system outlet conduit 5 b and gas storage vessel coolant inlet valve 5 e. The chilled coolant flows past valve 5 e and into gas storage vessel heat exchange conduit 11.

As best shown in FIG. 1, heat generated by filling gas storage vessel 13 with the gas is removed by coolant fluid traversing conduit 11. The warmed coolant fluid returns to cooling system 17 via gas storage vessel coolant outlet valve 7 e, warm coolant fluid fitting 7 c, cooling system inlet conduit 7 b, and cooling system inlet valve 7 a. The cooling system also includes a pump, which one of ordinary skill in the art will recognize may be located anywhere along the coolant fluid path, and an expansion tank serving as a reservoir for coolant fluid and buffer for moderating pressure fluctuations in the coolant fluid path.

In the FIG. 1 embodiment, coolant fluid from the internal combustion engine 19 is separately cooled by radiator 21.

In an alternative embodiment and as best illustrated in FIGS. 2 and 3, the vehicle 1 need not have an onboard cooling system 17. Rather, the coolant fluid may be chilled with vehicle radiator 21. In this case, chilled coolant fluid is pumped from radiator 21 through chilled coolant outlet conduit 6 and warmed coolant fluid returns to radiator 21 via warm coolant inlet conduit 8.

As more particularly shown in FIG. 3, during a filling operation second radiator valve 25 is actuated to prevent flow of coolant from second radiator hose 32 to radiator 21 while allowing coolant flow from warm coolant inlet conduit 8 to radiator 21. Also, first radiator valve 31 is actuated to prevent flow of coolant from radiator 21 to first radiator hose 33 while allowing coolant flow from radiator 21 to chilled coolant inlet conduit 6. In this manner, warm coolant from the gas storage vessel 13 flows through warm coolant inlet conduit 8 and into radiator heat exchange conduit 27 where it is cooled with the fan. Chilled coolant then flows to the vessel 13 via coolant inlet conduit 6.

Conversely, in between fills the engine may be cooled by actuating second radiator valve 25 to allow flow of coolant from second radiator hose 32 to radiator 21 and prevent flow of coolant from warm coolant inlet conduit 8 to radiator 21. Also, first radiator valve 31 is actuated to allow flow of coolant from radiator 21 to first radiator hose 33 while preventing coolant flow from radiator 21 to chilled coolant inlet conduit 6. With first and second valves 25, 31 in these latter orientations, coolant from engine 19 may be cooled at radiator 21.

For obvious reasons, one of ordinary skill in the art will recognize that, in the embodiment of FIGS. 2 and 3, the conduits, valves, and fittings on the vehicle associated with the coolant path of the gas storage vessel need not be specifically disposed in the locations illustrated by the Figures. Rather, they may be located anywhere on the vehicle 1 so long as they suitably perform their functions.

While not depicted, a temperature control system is advantageously used to control the coolant fluid flow with a coolant fluid pump in order to provide the proper cooling rate while filling the storage vessel 13. Also, one of ordinary skill in the art will recognize that the coolant removing heat from the storage vessel 13 may be cooled by both the cooling system 17 of FIG. 1 and the radiator 21 of FIGS. 2-3 whether in parallel or in series. The various combinations of conduits, valves, and manifolds needed to achieve these alternative cooling schemes are well within the knowledge of the ordinarily skilled artisan.

Both refrigeration system and radiators are suitable for use as the cooling system. The heat exchange surface area and cross-sectional dimension of the cooling conduit of the cooling system (or radiator in the case of the embodiment of FIGS. 2-3), the diameter of the cooling system outlet and inlet conduits, and the heat exchange surface area and cross-sectional dimension of the gas storage vessel heat exchange conduit may be sized to accommodate the cooling capacity required for filling a gas storage vessel at a certain mass flow rate. It is well within the knowledge of one of ordinary skill in the art to utilize existing heat exchange models in engineering texts in designing the cooling system. In the case of the heat exchange conduit of the gas storage vessel, it is also well within the knowledge of one of ordinary skill in the art to utilize existing teachings on heat exchangers for use with gas adsorbent or absorbent systems.

For hydrogen storage vessels containing metal hydride absorbent material in particular, the patent literature is replete with teachings of suitable vessel and heat exchanger designs such that their details need not be duplicated herein. Representative ones include published U.S. patent application US 2005/0211573, published Japanese patent application JP63-035401 A, and U.S. Pat. Nos. 4,609,038; 6,709,497; 6,708,546; 6,666,034; 6,638,348; 6,530,233; 6,432,379; 6,267,229; and 6,015,041.

For silane storage vessels containing a zeolite material as an adsorbent, one of ordinary skill in the art may advantageously utilize the teachings of U.S. Pat. No. 6,660,063.

Alternatively, the required cooling capacity of the gas storage vessel may be empirically determined and the cooling system selected according to the determined capacity. In such a case, empirical testing may be designed according to an estimated required cooling capacity. The estimated required cooling capacity may be roughly calculated by multiplying the molar heat of enthalpy of the sorption reaction between the gas and the sorbent material (which is well known in the art) by the mass flow rate (in moles per unit time) of the gas. Based upon this rough estimate of the cooling capacity of the gas storage vessel, an off-the-shelf refrigeration system or radiator with rated cooling capacity may be selected. The suitability of such a selected cooling system may be easily and empirically determined by filling the gas storage vessel while monitoring its temperature. As an example, filling a 200 Nm³ FeTi hydride storage tank in one hour would require a cooling power of 75 kW. As further examples, filling a 10, 800, or 1,300 Nm³ FeTi hydride storage tank in one hour would require a cooling power of 4, 300, or 500 kW, respectively. This is well in the ability of current radiators used in trucks having a 150-250 kW power engine. In the case of the embodiment of FIGS. 2-3, the vehicle radiator may be over-sized to accommodate the required cooling capacity of both the internal combustion engine while running and the gas storage vessel during filling. Preferably, the cooling system (or radiator in the embodiment of FIGS. 2-3) has a cooling power of about 2-500 kW, and more preferably about 50-150 kW.

It should be noted that in each of the embodiments, the vehicle 1 is propelled by combustion of a hydrocarbon fuel in fuel tank 20 by internal combustion engine 19.

Also, for safety reasons, the cooling system 17 or radiator 21 and associate pump(s) are best powered by electricity either from the vehicle's battery or other suitable electrical power source.

Preferred processes and apparatus for practicing the present invention have been described. It will be understood and readily apparent to the skilled artisan that many changes and modifications may be made to the above-described embodiments without departing from the spirit and the scope of the present invention. The foregoing is illustrative only and other embodiments of the integrated processes and apparatus may be employed without departing from the true scope of the invention defined in the following claims. 

1. A method of filling a gas storage vessel, comprising the steps of: allowing compressed gas to flow from a compressed gas storage tank borne by a compressed gas delivery vehicle to a gas storage vessel where it is sorbed by a sorbent material contained therein, wherein the gas storage vessel is not borne by the vehicle; and allowing a primary coolant fluid to flow through a primary coolant path circulating between the gas storage vessel and a primary cooling system borne by the vehicle thereby cooling the sorbent material.
 2. The method of claim 1, wherein the sorbent material is a metal hydride and the gas is hydrogen.
 3. The method of claim 1, wherein the gas is silane and the sorbent material is a zeolite.
 4. The method of claim 1, wherein a secondary coolant flow path extends between an internal combustion engine of the vehicle and a vehicle radiator and said primary and secondary coolant flow paths do not fluidly communicate.
 5. The method of claim 1, wherein a secondary coolant flow path extends between an internal combustion engine of the vehicle and the primary cooling system and the primary cooling system is a vehicle radiator.
 6. The method of claim 5, further comprising the steps of: providing first and second valves adapted and configured to selectively allow flow of the primary coolant through the primary coolant flow path or the secondary coolant flow path; and actuating the first and second valves to place them in orientations that either: allows a flow of the primary coolant through the primary coolant flow path or the secondary coolant flow path, or allows a flow of the primary coolant through the primary coolant flow path or the secondary coolant flow path.
 7. The method of claim 2, further comprising the step of allowing a flow of hydrogen from the hydrogen storage vessel to a stationary hydrogen consumption device, wherein said stationary hydrogen consumption device is not borne by the vehicle.
 8. The method of claim 2, wherein the primary coolant is pumped by a pump utilizing electrical power while an internal combustion engine used to propel the vehicle is not running. 